Supply circuit for a pair of hot cathode fluorescent discharge lamps



Nov. 26, 1963 SUEHIRO AOKI 3,112,427

SUPPLY CIRCUIT FOR A PAIR OF HOT CATHODE FLUORESCENT DISCHARGE LAMPS Filed Aug. 17, 1961 INVENTOR. SUEHIRO AOKI ,BYflMv M' United States Patent 3,112,427 SUPPLY CIRCUIT FOR A PAlR 0F HOT CATHQDE FLUORESiIENT DISCHARGE LAMPS Suehiro Aoki, 53 Shimonegishi-cho, Daito-ltu, Tokyo, Japan Filed Aug. 17, 1961, Ser. No. 132,158 1 Claim. ((11. 31597) This invention relates to improvements in a supply circuit for a pair of hot cathode fluorescent discharge lamps, and more particularly to a circuit leading toflickerless lamp operation.

One obiect of this invention is to provide a supply circult whereby it is possible to light a pair of fluorescent discharge lamps flickerlessly using a single leakage transformer without the need for two magnetically independent transformers in the previously known manner.

Another object of this invention is to provide a Supply circuit for flickerless starting of a pair of fluorescent discharge lamps having similar wave dorms, brightnesses, and life, as far as possible.

Still another object of this invention is to provide a means whereby it is possible to start instantaneously a pair of fluorescent discharge lamps without such lamps being particularly designed for rapid start.

Still another object of this invention is to provide a pair of fluorescent discharge lamps which require less material for the manufacture and less labor for the assembly thereof.

Further objects of th invention will appear from the following description when read in connection with the accompanying drawings showing an illustrative embodiment of the invention and wherein:

PEG. 1 is a schematic diagram of a supply circuit for a pair of lamps in accordance with this invention whereby it is possible to start the lamps flickerlessly and rapidly without such lamps being particularly designed for rapid start; and

FIG. 2 is a circuit diagram of a supply circuit of the well known type for a pair of lamps which is fiicker less but not of the rapid start type.

Similar numerals refer to similar parts throughout the two diagrams.

Refen-ing now to FIG. 1, an alternating voltage source 2 is supplied at terminals l and 1. There are provided a core 3 of a leakage transformer and a winding 4 of an autotransformer part wound on the core =3 of the leakage transformer. The winding 4- has a primary winding P which is formed by taps and 17, and a secondary windlugs 3 and S the secondary winding S being arranged on the left of the tap and the secondary winding 3 eing arranged on the right of the tap 1'7. Intermediate tap 5 at the electrical midpoint of the primary winding P is connected to one end of a secondary winding 6 of the leakage transformer part wound on the core 3. The leakage transformer part also has another secondary wind- 7 wound on the core 3; and coil S is wound on the core 3 and is connected across a hot cathode of a fluorescent lamp 32, in order to supply cunrent to heat cathode 15. Another coil for heating another hot cathode '13 of another fluorescent lamp 11 is shown as a winding arranged on the right of a tap 24 of the secondary winding '7 of the leakage transformer part, cathode 13 being connected across said winding. The fluorescent discharge lamp 11 is of phase lag while the fluorescent discharge lamp 12 is of phase advance. Numeral represents metal plates arranged adjacent to the lamps 11 and 12.. Numeral 26 represents an optional condenser connected on one side to both plates 25 and on the other side to tap 17. The fluorescent discharge lamp 11 has hot cathodes 13 and 14 while the other lamp 12 has hot cathodes 15 and 16.

3d EZAZ? Patented Nov. 26, 1%63 There is a phase advancing condenser 10, one side of which is connected with one end of said secondary winding 6 of the leakage transformer part, and the other side of which is connected to one end of winding 8.

By way of example, when the primary winding P of the autotransformer 4- has 680 turns, one secondary winding S of the autotransformer part has 200 turns; the other secondary winding S has turns; one secondary winding 7 of the leakage transformer part has 850 turns; the winding from the tap 24 to the right end of the secondary winding 7 has 38 turns; the other secondary winding 6' of the leakage transformer part has 900' turns; and the coil 8 for heating the hot cathode 15 has 20' turns.

Using a pair of 4-0 watt discharge lamps in this arrangement, which are not of specially designed rapid start type but of usual type, when they are energized, there is a voltage of about 230 volts between the terminal 1 and the left end of the secondary winding 6 of the leakage transformer, which is supplied to the discharge lamp 12. while the hot cathode 15 at the left end of the discharge lamp 12 is heated rapidly by the cathode heating coil 8. In this case about 456 rnilliamperes of current flow across the heating coil 3. Meantime, the hot cathode 1d at the right end of the discharge lamp 1% is heated by the secondary windning S of the auto-transformer 4, and the discharge lamp 12 lights up rapidly.

In this case, there is a voltage of about 230 volts between the terminal 1 and the tap 24 of the secondary winding '7 of the leakage transformer and a. voltage of about 235 volts between the terminal 1 and the right end of the secondary winding '7 of the leakage transformer.

At first a current of 598 to 600 milliamperes iiows across this secondary winding 7. Soon, accompanied by the li hting of the discharge lamp ii, the current flowing across the discharge lamp is reduced to about milliamperes.

I have found through experiments that it is possible to select a comparatively small value for resistances of the phase advancing discharge lamp 12, since the discharge lamp i2 is connected with the secondary winding 6 which is extended from the intermediate tap 5 arranged at the electrical mid-point of the primary winding P of the autotransformer 4, together with the condenser 19 in series. As a result, it is possible to equalize the wave forms, brightnesses, and lives of the two fluorescent discharge lamps 11 and 12.

As further features, the secondary winding S of the autotransformer 4 serves as the heating coil for the hot cathodes 14- and 16 at one end of the two discharge lamps 11 and 12., respectively. Also, as pointed out above, the secondary winding 7 connected magnetically with the autotransforrner has the tap 24 which is connected with the hot cathode 13 of the other end of the discharge lamp 11, so that the right part of the secondary winding 7 (beyond tap 24) serves as the heating coil for the hot cathode 13. Also, as pointed out above, another secondary winding 6 connected magnetically with the autotransformer is connected with the hot cathode 15 of the other end of the other discharge lamp 1?. across the phase advancing condenser lh. As a result, it is possible to carry out rapid starting flickerlessly without using a discharge lamp spe cially designed for rapid starting, for example, having an inner surface of the tube coated with silicone.

In the arrangement of a flickerless starter of the conventional type as shown in FIG. 2, there is provided a core 18 for a leakage transformer. Primary winding 19 of the leakage transformer wound around the core 18 has a tap 29. The winding 19 to the right of tap 20 is connected across the two hot cathodes M and 15 of two fluorescent discharge lamps 11 and 12, respectively, for heating purposes secondary winding 21 is wound around the core I18. Another core 22 of a choke coil is provided and is magnetically independent of the leakage trans former. (lhoke coil 25 is wound around core 22.

As will be seen from comparison of FEGS. 1 and 2, while it is suiiicient to provide a single leakage transformer having a core 3 in the arrangement of the first embodiment, it is necessary in the second embodiment to provide a leakage transformer having a core around which a secondary winding 1 is wound and in addition a choke coil having a core 21 around which coil 23 is wound and which is magnetically independent of the leakage transformer.

in the arrangement shown in FIG. 2, the primary winding 19 of the leakage transformer having the core 18 is connected with the secondary winding 21 in series. Winding 21 is further connected with choke coil 23 in series, and coil 23 is still further connected by cond nser 18 to a central tap of a further leakage transformer winding 8. Winding 8 is connected across the other cathode 13 of lamp ill. Still anotr er leakage transformer winding 9 is connected across the other cathode L; of lamp 12.

l. have found through experiments that when the arrangement shown in FIG. 1 is energized, the hot cathode of the two discharge lamps 1i and 12 are heated within a relatively short period so that a sufficiently intensive voltage is supplied to the lamps for starting discharge, and fiickerless lighting is continued.

While in the arrangement shown in FIG. 1, since the two discharge lamps l1 and 12 employ the primary winding P of the autotransformer 4 of the leakage transformer in common, tests have shown that there is no problem of discharge of one of the two discharge lamps just after the other lamp has discharged.

For the arrangement of the well known type as shown in FIG. 2, since it is required to provide a leakage transformer raving a core 18 and a choke coil having another core 22 even if the lamp is not of a rapid starting type,

assembling and modulation of the circuit are about three times as laborious as in the case of the arrangement shown in F 1G. 1. Specifically, the individual cores require modulation therefor, respectively, and in addition the assemblage also requires modulation therefor, while the single leakage transformer of FIG. 1 requires only a single modulation therefor. Furthermore, the arrangement shown in P16. 2 requires more cores, fittings, wire, etc., than that of PEG. 1 whereby the former becomes expensive. if the labor costs are added, the arrangement as shown in FIG. 2 becomes about four times as expensive to produce as the arrangement shown in FIG. 1.

It will be apparent that various changes, omissions and additions in the invention may be made without departing from the scope and spirit thereof.

Va"; at I claim is:

A flickerless supply circuit for a pair of fluorescent discharge lamps having cathodes, comprising an autotransformer part having two secondary windings and a leakage transformer having two secondary windings, said four secondary windings being Wound around a common core, said antotransformer part having a primary winding having an intermediate tap arranged at its electrical mid point, said intermediate tap being connected with one of the leakage transformer secondary windings, said one of said leakage transforms" secondary windings being connected with a terminal of a cathode of one of said pair of fluorescent discharge lamps across a phase advancing condenser, the other cathode of said one lamp and a cathode of the other of said lamp pair being in common connected across one of said auto-transformer secondary windings, and the other of said auto-transformer secondary windings being connected with the other cathode of said other lamp of said pair across the other of said leakage transformer secondary windings.

No references cited. 

